The invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.
Percutaneous access devices, hereinafter referred to as PADs, are employed to establish a connection through the skin between an organ or device implanted within the human body and some external device. The present invention is especially concerned with PADs which are implanted on a long-term basis.
Although a substantial amount of research on devices of this type has been undertaken in recent years, the prior art in general has failed to adequately solve recurring problems of both mechanical and biological nature.
A basic problem confronted by such devices is that they must protrude through the skin, and the outer layer of skin or epidermis must necessarily be provided with an opening for such purpose. The epidermis has a natural propensity to attempt to close such unnatural openings and will attempt to externalize the embedded device by epidermal cell proliferation, resulting in marsupialization, or sinus-tract formation when marsupialization is not complete. Marsupialization tends to extrude the implanted device, while sinus-tract formation provides ideal conditions for the development of infection. Likelihood of infection can also occur upon displacement of the PAD relative to the skin which tears or ruptures the bond between the skin and protruding portion of the PAD.
It has been pointed out by Winter (see Transcutaneous Implants: Reactions of the Skin Implant Interface--J.Biomed.Mater.Res Symposium 5:99, 1974) that basal cells of the epidermis do not invade the underlying dermis layer under normal conditions and are probably prevented from doing so by collagen fibers in the dermis. This suggested the possibility of blocking downgrowth of the epidermis along the side of the implanted device if the dermis could in some manner be firmly bonded or interlocked to the device to form a barrier.
The present invention is especially directed to methods and apparatus for forming such a barrier.